MATHEMATICAL NOTES. 159 



' 



l&c 



] 

 > 



+ &c. by Taylor's theorem. 



Now, when 2J 1 =2J 2 =&c.=0, the coefficient off (p} a will vanish 

 if p> n. And whatever the values of z, the coefficient off (p} a 

 vanishes if p <n: for we know that 





 " ' 



being < n, and = 1 when & = w ; 



which was to be found. 



